Animals and Plants which do not currently exist on real-life Earth

Animals

Plants

"Ironwood" is a general term used in real-life to refer to a wide variety of tree species - it isn't clear if "Ironwood" in Westeros is supposed to be one of these real-life analogues, or if it is, which one.

Animals and Plants which are currently found on real-life Earth

Note: a few of these are significant enough within the story to merit their own article (such as "Horses"), but most do not. Sheep in Westeros are the same as sheep in real-life. This section is a cited list of different animals and plants specifically mentioned in dialogue in the TV series.

Also, this list does not contain animals and plants which have only been observed in Heraldry - because some heraldry contains mythical animals, but that isn't proof that they "exist" in their world (i.e. a mermaid appearing in heraldry can't be taken as proof that mermaids exist).

South of the Riverlands in Westeros, particularly in the Reach, trees shift to being predominantly maple, elm, beech, and poplar, with a few willows as well. [37]

In the books

The existence of New World Crops in Westeros poses a confusing issue, because it is loosely based on the medieval British Isles (and Essos is based on Eurasia in general, and Sothoryos is loosely analogous to Africa). Tobacco specifically is not present in Westeros: instead people chew the leaves of a plant known as "sourleaf", which is much like chewing tobacco, but not quite the same as it stains teeth blood-red. Nonetheless, the novels actually have sporadically mentioned New World animals and plants in Westeros which are anachronistic to a medieval European setting: Arya is described as eating maize-corn in the second novel (ears of corn roasted in their own husks), and Dornish fire peppers are described as being stuffed - indicating that they are New World style bell peppers, not just the pepper spice. Potatoes are never mentioned in the novels: the TV series has casually mentioned potatoes several times, but given that even maize-corn and bell peppers incontrovertibly exist in Westeros as well, this might not actually be a drastic change.

One detail that the TV series has not mentioned so far is that the Aurochs is still alive and commonly raised as a domesticated animal. Aurochs were the precursor of modern cattle breeds, but were much larger than them, comparable to the difference between a direwolf and a common grey wolf. In real life, aurochs were not even Pleistocene megafauna the way that dire wolves and mammoths were: the last pure-strain aurochs died in 1627. It is recorded that the dragon Balerion the Black Dread grew so large that he could swallow an aurochs whole. Grenn is nicknamed "Aurochs" by his fellow recruits in the Night's Watch, due to his large size and slow speed (comparable to calling him "Ox").

Popular myths say that unicorns live on the island of Skagos, a barbarous large isle off the east coast of the North but which only gave nominal allegiance to Winterfell (much of Skagos actually extends north of where the Wall is on the mainland). There is a small kernel of truth to this, but the "Skagosi Unicorn" is essentially just an enormous one-horned species of goat.

Syrio Forel mentions to Arya Stark that the Sealord of Braavos maintains a menagerie of exotic animals collected from the far corners of the world (perhaps, by being sold from one trader to another, from well beyond the regions of the world known to men in Westeros and the Free Cities). Forel describes seeing giraffes and thylacines in the menagerie - though where they originally came from is unknown (perhaps even to the Sealord). Forel gives a literal description, as the words "giraffe" and "thylacine" do not exist in their world:

"Hear me. The ships of Braavos sail as far as the winds blow, to lands strange and wonderful, and when they return, their captains fetch queer animals to the Sealord's menagerie. Such animals as you have never seen, striped horses, great spotted things with necks as long as stilts, hairy mouse-pigs as big as cows, stinging manticores, tigers that carry their cubs in a pouch, terrible walking lizards with scythes for claws. Syrio Forel has seen these things." (A Game of Thrones, Arya IV)

The thylacine (also known as the "Tasmanian tiger") was a large striped marsupial found in Australia, which was driven to extinction in the early 20th century. They somewhat resembled wolves or predatory big cats, but this is simply due to convergent evolution as apex predators. Thylacines therefore basically resembled "tigers that carry their cubs in a pouch". Thylacines are not extinct in Martin's fictional world, though they don't seem to be native to Essos, instead coming from lands far beyond it.

Other than this one example by Syrio (of very exotic animals from far-away continents), there has been no mention of other animals endemic to the Americas or Australia, such as any other marsupials or monotremes. Opossums have never been mentioned, nor have raccoons, skunks, jaguars, etc.

Monstrously large animals exist in the unexplored deep jungles of Sothoryos, but they are half-legendary and considered very exotic in Westeros or the Free Cities. Dinosaur-like reptiles actually exist in the southern unexplored jungles of Sothoryos - though they are incredibly exotic and semi-legendary to peoples in Westeros and Essos. There are reports of raptor-like dinosaurs in southern Sothoryos, that run down their prey and rip them apart with long, curved claws on their hind legs. Their existence is confirmed to be more than mere legend by Syrio's account that he saw captive specimens of such "walking lizards" in the Sealord's private zoo.

Several large animals species which in real life are from Africa or Asia don't exist in Westeros (which is based on the British Isles) but are found in the other continents. Elephants and camels are often found in Slaver's Bay - though whether they are native or were originally introduced from somewhere else is unclear. Animals from the western end of Essos around the Free Cities tend to be more like this from Europe: elephants are rarely encountered there, with the very notable exception of Volantis, which is the southern-most of the Free Cities and closest to Slaver's Bay. Other large African animals such as rhinos and ostriches haven't been mentioned in the first five novels, though given that other large African animals such as elephants are found in Essos, they might plausibly exist somewhere. Zebras can be found in humid lands of southern Yi Ti.

As George R.R. Martin himself has pointed out, Heraldry used in the story isn't always a good guide for what animals exist in his fantasy world, because characters sometimes use heraldry which contains creatures which are mythical to them, within the storyverse. For example, Martin cited that one minor character actually uses a winged pig as his personal sigil - but flying pigs are not a real animal within the world of Westeros.

↑"Kissed by Fire": "...Provisions, so this city might survive the winter: a million bushels of wheat, half a million bushels each of barley, oats, and rye, 20,000 head of cattle, 50,000 head of sheep." - Olenna Tyrell

↑"If the half man betrays us, Shagga Son of Dolf will cut off his manhood - " "- 'and feed it to the goats', yes." - Shagga and Tyrion, "The Pointy End"

↑According to a production blog post, a live lemur appears in Season 5 in a market in the Free Cities. Lemurs are actually present in the novels: they can be found in the Forest of Qohor, at the eastern edge of the Free Cities. Lemurs are otherwise rarely seen so far north, and mostly live in the Summer Isles and Sothoryos.